In recent years, in mounting of an IGBT module, the integration density has been increasing. When an externally leading terminal of a package is mounted on a conductive pattern-bearing insulation substrate, there are demands for the junction strength between the externally leading terminal and the conductive pattern-bearing insulation substrate, and the reliability of the junction part thereof. Further, when the externally leading terminal of the package is mounted on an insulation substrate including a conductive pattern (circuit pattern) formed thereon (which will be hereinafter referred to as a conductive pattern-bearing insulation substrate), there is also still another demand for the positional precision on the layout of the externally leading terminal.
The IGBT module is configured such that a conductive pattern-bearing insulation substrate is mounted on a heat radiation base plate, and such that an externally leading terminal and a semiconductor chip are soldered on the conductive pattern-bearing insulation substrate. As the externally leading terminal to be soldered onto the conductive pattern of the conductive pattern-bearing insulation substrate, there is often used an independent terminal not fixed to a resin case. Whereas, when an external wire and an independent terminal are electrically connected, there is used a nut glove formed of a resin body in which a nut is fitted into a nut receiving part (see e.g., the following Patent Documents 1 to 3).
Then, a configuration of a related-art IGBT module will be described. FIGS. 12A and 12B are each an explanatory view showing the configuration of a related art IGBT module. FIG. 12A is a plan view of the essential part of the related art IGBT module 500 as seen from the top surface thereof. FIG. 12B is an essential part side cross-sectional view cut along line X-X of the IGBT module 500 of FIG. 12A as seen from the direction of an arrow orthogonal to the line X-X. In the IGBT module and each member forming the IGBT module, the top surface is on the resin case side, and the bottom surface is on the heat radiation base plate side.
FIGS. 13A to 13C are each an explanatory view showing the configuration of the nut glove of FIGS. 12A and 12B. FIG. 13A is a plan view of an essential part of a nut glove 58 as seen from the top surface thereof. FIG. 13B is a side view of the essential part of the side surface of the nut glove 58 of FIG. 13A as seen from the direction of an arrow P orthogonal to the line X-X. FIG. 13C is an enlarged perspective view of a projection part 60 provided on each side surface of the nut glove 58. FIG. 14 is a cross sectional view showing an essential part of the independent terminal soldered on the conductive pattern-hearing insulation substrate. FIG. 14 is a cross sectional view of the side surface of the IGBT module 500 shown in FIGS. 12A and 12B as seen from the direction of an arrow K in parallel to the line X-X.
In assembly of the related-art IGBT module 500, first, a conductive pattern-bearing insulation substrate 53 is soldered on a heat radiation base plate 51. Then, an independent terminal 55 is soldered on the conductive pattern of the conductive pattern-bearing insulation substrate 53. Then, a resin case 56 is put in such a manner that the top surface of the independent terminal 55 is exposed outside the resin case 56. Thus, the bottom of a sidewall 56a of the resin case 56 is bonded to the periphery of the heat radiation base plate 51. Then, the nut glove 58 is inserted and set (below, provided in an inserted manner) through an opening 57 formed in the resin case 56 so as to lie under the independent terminal 55. The opening 57 is formed in the sidewall 56a and a partition plate 62 in the resin case 56. The nut glove 58 is a resin body in which a nut 58a is fitted into a nut receiving part 58c provided on the top surface, and is in the shape of a rectangular parallelepiped (in the shape of a rod). The nut 58a fitted in the nut receiving part 58c is vertically movable in the nut receiving part 58c. 
The independent terminal 55 is in an inverted U shape in cross section as shown in FIG. 14. In the top (the bottom of the U shape) exposed outside the resin case 56, there is formed a mounting hole 55a to be mounted to an external wire. Whereas, the two legs (the opening ends of the U shape) of the independent terminal 55 are soldered to the conductive pattern-bearing insulation substrate 53. Further, a control terminal is also soldered to the conductive pattern-bearing insulation substrate 53.
The nut glove 58 is provided so that the nut glove 58 lies in the U-shaped hole of the independent terminal 55, and so that the nut 58a is situated immediately under the mounting hole 55a formed in the independent terminal 55. Each side surface 58b in parallel to the line X-X of the nut glove 58 is provided with a projection part 60 for fixing the nut glove 58 to the resin case 56. This results in a structure in which the projection part 60 prevents the nut glove 58 from coming out of the resin case 56.
The projection part 60 is, as shown in FIG. 13C, in the shape of a trapezoidal prism with a taper 61 in the direction of insertion of the nut glove 58 shown by an arrow N, and is structured to be easily inserted into the resin case 56. Incidentally, the size of the projection part 60 is several millimeters at the bottom thereof, and the height of the projection part 60 is at the order of 0.1 mm. The bottom of the projection part 60 is a portion contacting with the side surface 58b of the nut glove 58. The height of the projection part 60 is the length projecting from the side surface 58b of the nut glove 58 in the direction perpendicular to the side surface 58b of the nut glove 58.
Patent Document 1: Japanese Patent Application Publication No. 2008-091787
Patent Document 2: U.S. Pat. No. 6,597,585
Patent Document 3: Japanese Utility Model Application Publication No. H5-15445
However, as shown in FIG. 13C, in the related-art nut glove 58, the rear end face 60a of the projection part 60 is perpendicular to the side surface 58b of the nut glove 58. The rear end surface 60a of the projection part 60 is the surface rearward in the direction of insertion of the nut glove 58, and is the surface opposite to the surface with the taper 61. Accordingly, after fitting the nut glove 58 into the resin case 56, a clearance T of about 0.3 mm is created between the rear end face 60a of the projection part 60 and the wall surface 62a of the partition plate 62. As a result, the nut glove 58 cannot be fixed to the resin case 56 so as not to be displaced from a prescribed position.
Therefore, when the clearance T occurs between the rear end face 60a of the projection part 60 and the wall surface 62a of the partition plate 62, the nut glove 58 moves rearward in the direction of insertion thereof (in the direction opposite to the direction of insertion thereof). This makes difficult the alignment between the nut 58a of the nut glove 58 and the mounting hole 55a of the independent terminal 55. As a result, it becomes difficult to perform an operation of fixing an external wire (not shown) and the independent terminal 55 by a bolt by means of an automatic machine.